Refrigerating apparatus



April 19, 1938. E. HEITMAN REFRIGERATING APPARATUS Filed Jan. 18, 1955 3 Sheets-Sheet 1 INVENTOR. EDWIYAPD l/awwn M K I g- M s ATTORNEY.

- April 19, 1938. E, H IT AN 2,114,766

REFRIGERATING APPARATUS Filed Jan. 18, 1955 3 Sheets-Sheet 2 I N VEN TOR. flax/44 1707mm.

ATTORNEY.

April 19, 1938. E'. HEITMAN REFRIGERATING APPARATUS Filed Jan. 18, 1955 3 SheetsSheet 3 a R. ,Y. )4 W 0 EM 0 a m M m 0 wk Patented Apr. 19, 1938 PATENT OFFICE REFRIGERATING APPARATUS Edward Heitman, Detroit, Mich., assignor, by

mesne assignments, to Nash-Kelvinator Corporation, Detroit, Mich., a corporation of Maryland Application January 18, 1935, Serial No. 2,387

Claims.

My invention pertains to refrigerating systems and more particularly to means for controlling the temperature of the cooling element of the system.

Refrigerating systems are normally operated so that a predetermined temperature is automatically maintained in the compartment to be cooled, but it is desirable to temporarily establish a modifled temperature condition for the purpose of removing ice and frost formed on the cooling unit by the moisture of the circulating air which condenses and freezes thereon.

. It is accordingly an object of my invention to provide a refrigerating system, which normally maintains a predetermined temperature in combination with modifying means for raising the upper limit of the predetermined temperature such means having a thermal responsive actuating means and a time measuring release'device whereby the modifying means is rendered effective to cause defrosting only at a time when the accumulation of frost and ice renders it desirable and. then only when a minimum of inconvenience will be caused thereby.

It is a further object of my invention to provide an automatic defrosting control for refrigerating system comprising a thermal actuator for actuating a defroster when a predetermined quantity of frost has accumulated on the unit in combination with a time measuring device arranged to release the actuated defroster for effective operation at a time of the day when the defrosting process will not greatly inconvenience the users of the refrigerating system.

The invention itself, however, both as to its organization and operation together with additional objects and advantages thereof will best be understood from the following description of speciflc embodiments when 'read in conjunction with the accompanying drawings in which:

Fig. 1 is a diagrammatic view schematically representing an automatic defrosting refrigerator system arranged in accordance with one embodiment of my invention; 7

Fig. 2 is an elevational view of a refrigerator showing a modified arrangement of thermobulbs for actuating the temperature control switch and the defrosting mechanism;

Fig. 3 is a diagrammatic view schematically representing a modified arrangement of my defrosting refrigerator system;

Fig. 4 is a sectional view taken on line IV-IV of Fig. 3 showing the slidable defrosting member in its uppermost position;

Fig. 5 is a similar view showing the defrosting member in its lower position; and

Fig. 6 is an elevational view of a refrigerator showing a modified arrangement of the thermobulbs for actuating the temperature control switch and the defrosting mechanism of the modified system, represented in Fig. 3.

Referring more specifically to Fig. 1 of the drawings, the apparatus comprises a heat insulating cabinet I for enclosing a food storage compartment 3, which is refrigerated by a cooling unit 5 mounted therein and supplied with refrigerant from any suitable source.

For illustrative purposes, I have shown my system arranged in conjunction with a compressionexpansion type of refrigerating system wherein the cooling unit 5 comprises an evaporator which is supplied with vaporizable liquid refrigerant from an adjacent compressor-condenser unit I, to which it is connected by suitable conduit means. One of the interconnecting conduits 9 comprises a suction line through which the compressor 1 draws the vaporized refrigerant, compressing it through condenser coils I I under high pressure to dissipate the latent heat of vaporization. From the condenser coils ll the liquefied refrigerant passes through a refrigerant line l3 to the evaporator unit 5 through a suitable enclosed float valve (not shown) or other suitable control means in accordance with the usual practice.

The evaporator 5 is maintained at a desirable normal temperature and in the present embodiment the refrigerant compressor 1 is driven by an electric motor H which is automatically controlled in accordance with the temperature in the compartment for the purpose of automatically maintaining the compartment temperatures within a predetermined range. For this purpose the energization of the motor I from the main line conductors LI' and L2 is controlled through an energizing circuit which is completed by the contacts of 'a thermally responsive switch l5. In the present embodiment, the switch is actuated directly in response to temperature variations.

The thermostatic temperature control switch l5 preferably comprises a snap acting toggle mechanism which consists of a shaft l1 slidably disposed in a bracket guide member I9 which is preferably mounted on a suitable controller panel 2|. Adjacent the upper portion of the slidable shaft H a peripheral groove 23 is provided which receives the inwardly directed ends ofa pair of toggle arms 25 and 21 which are drawn together..- to clamp the slidable shaft I! by biasingsprings 29 tensioned therebetween on opposite sides of the shaft. The outwardly directed end of each of the toggle arms passes freely between a pair of spaced guide pins 35 projecting from the panel 2i. One of the toggle arms 2'17 is provided with an extended end portion on which an electric contact bridging member 33 is supported by a suitable insulated bracket 35.

When the shaft ll andthe associated toggle arms are snapped to their uppermost position, as shown, the contact bridging member 33 is snapped down into bridging engagement on a pair of stationary electric contacts 36 which are adjacently supported on the panel board. In this position one side of the motor energizing circuit is completed from the main line conductor Ll through contacts 36 and a conductor SI to the motor it]. The other line conductor L2 is connected directly to the other terminal of the motor The slidable toggle shaft ll of the thermostatic switch it is reciprocatably actuated by means of a lever M having one end pivotally journalled on a stationary pin t?) in the panel board 2!] and the other end extended through a relatively large slot 65 in the shaft. A biasing spring t? is continuously compressed 'between the upper side of the pivoted lever ti and an adjustable stop member at whereby a biasing pressure is applied continuously to the lever. The adjustable stop 19 is mounted on the end of a threaded shaft 58 which screws through a stationary bracket and carries a knurled knob 55 on its opposite end whereby it may be adjusted to vary the operating characteristics of the thermostatic control switch l5. For actuating the pivoted lever ill in accordance with the temperature variations in the refrigerated compartment, a flexible metal bellows 5'8 is mounted on a suitable bracket 59 on the panel with a bearing ti on its free end pressing against the lower side of the pivoted lever ll opposite the biasing spring ll. Through a suitable interconnected conduit .varying pressures are applied within the flexible bellows 571 in accordance with the varying pressures set up within a thermo bulb 555 which contains a volatile or expansible I liquid and which is mounted within the com partments. By manipulating the adjustable stop member as to suitably adjust the tension on the biasing spring ill, and by selecting a suitable liquid for the thermo-bulb the thermostatic control switch US may be adjusted for operating the compressor I to maintain a predetermined temperature range in the compartment.

In operation, when increasing pressures are set up in the thermo-bulb E55, by increasing temperatures in the compartment, the flexible bellows ill is thereby expanded lifting the shaft ll above the center position of the toggle arms 25 and ill whence it is snapped upwardly, as shown. In this position, the electric motor i3 is energized and drives the compressor I, to supply liquefied refrigerant to the evaporator b within the compartment. When the temperature has been sufficiently reduced, the pressure within the flexible bellows 5? is also decreased and the biasing spring 4'! rotates the pivoted lever ll clockwise turning the toggle arms below the center line position. When this takes place the associated biasing springs 29 snap the toggle arm downwardly to an inverted position thereby moving the electric bridging contact 33 away from the stationary contacts 36 and interrupting the motor energizing circuit. A stop-member El may be provided on the panel 2| for limiting the downward movement of the slidable shaft l1.

In order to modify the normal operating temperature of the system for the purpose of melting off the ice and frost accumulated upon the cooling unit 5, I have provided a defrosting mechanism I comprising a device for adding an auxiliary biasing pressure upon the thermostatic control switch 95 to thereby modify its normal operating characteristics by increasing its upper or opening temperature limit.

As shown, the modifying means comprises a second snap acting mechanism which includes a second toggle shaft, or defrosting member 1|, slidably disposed in a bracket E3 on the panel in alignment with the first toggle shaft ll of the thermostatic switch B5. A pair of defrosting toggle arms l5 and II are urged in gripping engagement on opposite sides of the slidable defrosting shaft It by suitable biasing springs 19. The free ends of the toggle arms extend between pairs of spaced guide pins til mounted in spaced relation on the panel. A pivoted actuating lever BI is journaled at one end on a stationary pivot 83 in the panel with its other end' extending through a relatively large slot 85 provided in the slidable defrosting member H. A stationary stop Bl projecting from the panel engages the upper edge of the pivoted actuator lever ill for limiting its uppermost position, as shown.

The operation of the defrosting mechanism 10, is controlled by a flexible metallic bellows 89 and a biasing spring til which are disposed in opposed oted defrosting lever ill in opposing relation to the biasing spring (ii. A conduit Mil extends from the flexible bellows 89 of the defrost mechanism to a defrost controlling thermo bulb I03 which is mounted in the compartment in direct thermal conductive engagement with. the cooling unit.

The operating characteristics of the defrosting mechanism Iii are selected by adjusting the biasing spring Si and by providing a suitable volatile liquid in the defrost bulb tilt whereby during normal operation of the refrigerator sumcient pressure is provided in the flexible bellows E9 to resist the force of the biasing spring ti on the pivoted defrosting lever ti, and to thus prevent the defrosting member It being snapped to its lower most position.

The movement of the defrosting member H to its lowermost position is normally prevented by a slidable latch I105 which engages the underside of a laterally projecting flange 00'! on the upper end of the slidable member H. The latch I05 is slidably mounted adjacent the path of the flange it'll on the slidable defrosting member II and it is normally projected to latching position by,.a rotatable cam wheel I09 engaging its inwardly directed end. The cam wheel I 09 is driven by a time measuring device, or clock, such for example as a synchronous electric clock motor 'notch H5 in the face of the cam and it is driven at a suitable speed ratio from the clock motor to complete its rotation, for exampleonpe in twentyfour hours.

When the releasing notch H5 on the time measuring device is carried under the end of the latch I05, (as shown) the latter is slidably drawn into the notch by a leaf spring II1 one end of which extends freely into a slot H0 on the lower surface of the latch and having its other end rigidly secured to the side of the time measuring device by a screw I2I or any suitable fastening means. The releasing notch H5 is so positioned that when the clock motor is properly started the notch passes under the latch to permit the defrosting member H to move to its defrosting position, if so actuated by the presence of a predetermined amount of ice on the cooling unit, at a time when the defrosting operation will not interfere with the normal use of the refrigerator. A manual control latch is also provided which comprises a slidable pin I23 in a stationary bracket I25 adjacent the upper end of the slidable defrost memberwhereby it may be continuously locked out if desired. This may be desirable, for example, when the householder is entertaining late, or for any reason, wishes to postpone the defrosting operation for a 24 hour period which is readily accomplished by depressing the knob I21 on the slidable mounted pin.

In operation, the normal temperature control thermo bulb 65, being disposed in the compartment 3 remotely from the cooling unit 5 is influenced by the average temperature therein .and it intermittently actuates the compressor 1 to maintain the compartment temperature within a predetermined range. As the frost and ice accumulates upon the cooling unit 5, it provides a heat insulating layer which has a blanketing effect thereon. The automatic control switch I5 then operates the compressor 1 for longer periods of time, and the cooling unit 5 is operated at lower temperatures, in order to maintain the predetermined temperature range within the compartment. This in turn decreases the temperature and likewise 'the, pressure in the defrosting bulb -I03 which is in direct thermal conductive engagement with the cooling unit 5. The flexible defrost bellows 89 associated with the defrost mechanism is thereby gradually contracted, and the force applied on the defrosting lever 8| by the biasing spring 9|, being less opposed'by the bellows, tends to force the lever and the slidable defrosting shaft 1| downwardly.

The adjustment is such that the unopposed force becomes great enough to move the slidable defrost member 1I below the center position of the toggle arms 15 and 11, when a predetermined thickness of ice has accumulated upon the cooling unit 5. As soon thereafter as the cam wheel I09 on the time measuring device releases the latch I05, the slidable defrosting member H is snapped downwardly upon' the end of the slidable shaft I1 of the thermostatic switch I5 thereby adding an increment of biasing force tending to hold the switch open. As previously set forth, the added biasing increment is so predetermined that the switch cannot close and start the compressor until the ice is melted from the cooling unit, and the time measuring device is arranged to initiate the defrosting operation at a convenient time.

When the ice on the surface of the cooling unit 5 has melted, the increased pressure set up in the thermo-control bulb 65 and in the defrost bulb I03 is sumcient to move both of the snap acting mechanisms to their uppermost positions, as shown. The defrost mechanism remainsin this position until the accumulation of a predetermined amount of ice causes the defrosting operation to be repeated, and in the interim, the normal operation of the thermostatic switch I5 continues to operate the compressor 1 intermittently for maintaining the predetermined temperature range in the food storage compartment 3.

My automatic defroster may also be utilized in conjunction with a refrigerating system wherein the normal temperature is regulated by mounting the normal control thermo-bulb 65 in direct conductive engagement with the cooling unit 5, as shown in Fig. '2. The defroster is then controlled'by mounting the defrost bulb I03 spaced apart from the cooling unit 5, a distance substantially equal to the thickness of ice and frost permissible thereon. In this arrangement the temperature operating characteristics both the defrosting mechanism and the thermostatic switch are suitably adjusted, as above set forth, for proper response to the normal and abnormal temperature conditions to which they are exposed, so that when the engagement of the ice on the cooling unit 5 with the defrost bulb I03 lowers its temperature relatively to that occasioned by its normal exposure to the air in the compartment the resultant contraction of the flexible defrosting bellows 89 unbalances the force opposing the biasing spring 9| on the defrosting lever 8I. After this condition arises the subsequent withdrawal of the latch I05 by the time measuring cam I09 releases the defrosting member H and initiates the defrosting operation at a convenient time, as above set forth. The device is so adjusted that the rising temperature restores it to normal operation when the .ice has melted from the cooling unit 5.

In Fig. 3, in which similar reference characters are applied to similar elements, I have shown another embodiment of my invention wherein a defrost member I30 is actuated by a flexible bellows I3I which is mounted above a pivoted actuating lever I32. The flexible defrost bellows I3I reacts between a stationary bracket I33 and the upper side of the pivoted lever I32 where it opposes a biasing spring I35 which reacts upwardly upon the lower side of the pivoted lever- The lower end of the biasing spring I35 rests upon a stop I31 which is supported upon the end of a shaft I39 threadably supported in a stationary bracket I4I for convenient adjustment.

In this embodiment of my invention, the pivotedlever I32, which actuates the slidable defrost ing member I30, is received in an opennotch I43 on the slidable member, as shown more clearly in Figs. 4 and 5. The slidable defrosting member I30 is preferably of non-circular cross-section, and the open notch I43 which is provided on the back of the slidable member adjacent the panel board, has a lower ledge with a square shoulder for operative engagement with the lever I32 and a bevelled upper edge. An inclined guide member I45 is provided adjacent the free end of the pivoted lever. As shown in Figs. 4 and 5, the lower end of the inclined guide member I45 is rigidly supported on a suitable bracket I41 mounted on the panel 2I with its vertically projecting end extending angularly adjacent the outermost side of the free end of the pivoted lever I32. The-lower portion of the guide I45 is adapted to flex the end of the lever I32 toward set forth.

In operation the defrost member iiiil is positively moved towards its defrosting position by increasing pressures applied in the flexible defrost bellows idi from the defrost bulb M33 which is mounted in the storage compartment 3 remotely from the cooling unit 5. The normal temperature control thermo-bulb 65 is mounted in direct thermal conductive engagement with the cooling unit, which is thus maintained within a predetermined temperature range.

As the ice and frost accumulates onthe cooling unit 5 it has an appreciable heat insulating efiect. This causes the temperature of the food storage compartment 3 to rise although the cooling unit 5 is maintained within a predetermined temperature range. Since the defrost bulb tilt? is exposed to the rising temperature conditions in the compartment 3 it applies higher pressures in the flexible defrost bellows 030. For this arrangement, the defrosting device is so adjusted that when the permissible thickness of ice has accumulated upon the cooling unit 5, sumcient pressure is provided to move the defrost member itlil below the center position from which position it is tripped down upon the switch shaft ill to hold it in open position and raise its closing temperature limit. As soon as the latch Hi5 is withdrawn by the clock, this force is released and the defrosting operation is initiated.

When the ice has melted from the cooling unit ii the temperature control bulb is exposed to a high temperature which sets up an unusually high presure in the flexible bellows Pill on the thermostatic switch. This causes the switch to snap to its circuit closing position thus starting the compressor l and simultaneously restoring the slidable defrost member 03b to its upper or off position. As the operation of the compressor 7! lowers the temperature in the compartment 3, the pressure in the defrost bulb M3 is decreased to normal and the pivoted lever 032 of the defrosting mechanism is moved to its uppermost position by the biasing spring 5535. The thermostatic switch [15 thereafter continues to intermittently operate the compressor i in its normal manner until the defrost member itil is again released by the rising temperaturev of the compartment and the defrosting operation is then repeated.

The defrosting device, shown in Fig. 3, may also be advantageousiy'utilized by arranging the defrost bulb m3 in close coupled thermal engagement with the cooling unit 5, as shown in Fig. 6, with the temperature control thermo-bulb 65 mounted in spaced relation from the cooling unit 5, a distance substantially equal to the permissive thickness of ice on the cooling unit.

The operating characteristics of the control switch and the defrosting mechanism are so adjusted that when the accumulating ice contacts the temperature control bulb 65, its temperature is lowered and the compressor 1 will not start. The temperature will then rise in both the compartment 3 and the cooling unit 5 but more rapidly in the latter, and the pressure rising rapidly in the defrost bulb I03 trips the defrost member I30 down on the switch which is now held open. When the ice has melted, the higher temperature sets up a higher than normal pressure in the control bulb 65 whereby the switch is tripped up thereby starting the compressor 1 and also restoring the defrost member i3d to its uppermost or off position. The temperature of the cooling unit 5 is quickly lowered thus reducing the pressure in the defrost bulb Hi3 and the pivoted lever H32 is moved upwardly by the biasing spring I35 while the operation of the thermostatic control switch I5 continues in the normal manner.

In the arrangements described above the defrosting member is controlled jointly by the time measuring device and the defrost bulb. It will be understood that the pressure for actuating the normal control switch may be taken directly from a suitable portion of the refrigerating system in accordance with the well known practice.

It will be seen that I have provided an automatic refrigerator defroster which is of simple construction and positive in its operation and which is controlled to automatically defrost a refrigerator only at a convenient time of the day when a predetermined amount of ice has accumulated on the cooling unit.

Aside from the specific embodiments of the invention herein shown and described, it will be understood that numerous details of the construction may be altered or omitted without departing from the spirit and scope of the invention as disclosed and claimed, and that I do not desire to limit the invention to the exact constructions herein set forth.

I claim:

1.. A control for a refrigerator comprising in combination, circuit closing contacts, a two-way snap acting mechanism for quickly moving said contacts to circuit making or breaking position, means for actuating said mechanism to either position comprising biasing means and thermal responsive means disposed to react upon said mechanism in opposing relation, a second twoway snap acting mechanism, a second biasing means tending to move said second mechanism to engage said first mentioned mechanism to modify its temperature response characteristics, latching means for holding said second mecha nism in disengaged position, a time measuring device arranged to actuate said latching means and release said second mechanismat regular time intervals to engage said first mentioned mechanism for modifying its temperature response characteristics, and additional thermal means arranged to oppose said second biasing means for restoring said second mechanism to disengaging position to thereby release said first mechanism for normal temperature response.

2. A refrigerating system comprising a compartment to be cooled, a cooling unit therein, electromagnetic means for controlling the supply of refrigerant to said cooling unit, controlling means for said electromagnetic means comprising the combination of circuit closing contacts, a twoway snap-acting mechanism for quickly moving said contacts to circuit making or breaking position, means for actuating said mechanism to either position comprising biasing means and thermal responsive means disposed to react upon said mechanism in opposing relation, 9. second two-way snap-acting mechanism, a second biasing means tending to move said second mechanism to engage said first mentioned mechanism to modify its temperature response characteristics, latching means for holding said second mechanism in disengaged position, a time measuring device arranged to actuate said latching means and release said second mechanism at regular time intervals to engage said first mentioned mechanism for modifying its temperature response characteristics, and additional thermal means arranged to oppose said second biasing means for restoring said second mechanism to disengaging position to thereby release said first mechanism for normal temperature response.

3. A refrigerating system comprising a compartment to be cooled, a cooling unit therein, means for circulating refrigerant through said unit to maintain the temperature of. said compartment between predetermined limits, modifying means for raising the upper limit of the regulated temperature comprising a thermal responsive element disposed in intimate thermal coupled association with said unit whereby the abnormally low temperature of said unit necessary to maintain a predetermined temperature in said compartment when the unit is covered with frost will actuate the modifying means, means for latching said modifying means in ineffective position, and a time measuring device for periodically actuating said latching means to release said modifying means at a convenient time for defrosting.

4. A refrigerating system comprising a compartment to be cooled, a cooling unit, means for circulating refrigerant through said unit, thermal regulating means for controlling said refrigerant circulating means to maintain the temperature between predetermined limits comprising a thermal responsive element disposed adjacent said unit and spaced therefrom a distance substantially equal to the permissible thickness of accumulated frost on said unit, modifying means for raising the upper limit of the temperature responsive characteristic of said thermal regulating means comprising a thermal responsive element disposed in intimate thermal coupled association with said unit to render said modifying means effective when the temperature of said unit rises above its predetermined operating range, means for latching said modifying means in an ineffective position, and a time measuring device for periodically actuating said latching means to release said modifying means at a convenient time for defrosting the unit.

5. A refrigerating system comprising a compartment to be cooled, a cooling unit therein, means for circulating refrigerant therethrough to maintain said unit normally between predetermined temperature limits, modifying means for raising the upper limit of the regulated temperature range comprising a thermal responsive element disposed in said compartment remotely from said unit whereby a predetermined rise of temperature in said compartment due to the blanketing effect of a predetermined quantity of accumulated frost on said unit will render said modifying means effective to defrost said unit, means for latching said modifying means in an ineffective position, and a time measuring device for periodically actuating said latching means to release said modifying means at a convenient time for defrosting the unit.

6. A refrigerating system comprising a cooling unit, means for circulating refrigerant therethrough to maintain said unit normally between predetermined temperature limits, modifying means for raising the upper limit of the regulated temperature range comprising a thermal responsive element disposed adjacent said unit and spaced therefrom a distance substantially equal to the permissible thickness of. accumulated frost on said unit whereby said modifying means is automatically actuated to defrost said unit,

only to a certain abnormal condition of the refrigerating system, retaining means for preventing the operation of the condition responsive means, and a time control device periodically operated for releasing the retaining means when the condition responsive means is operable in response to said certain abnormal condition.

8. A refrigerating system comprising in combination, a cooling unit, means for circulating refrigerant through said unit, control means tending to maintain a predetermined temperature, means when operative being adapted to vary the operation of the control means and being responsive only to a certain abnormal condition of the refrigerating system, retaining means for preventing the operation of the condition responsive means, and a time control device periodically operated for releasing the retaining means when the condition responsive means is operable in response to said certain abnormal condition.

9. A refrigerating system comprising in combination, a cooling unit, means for circulating refrigerant through said unit and operable to tend to maintain a predetermined temperature of the cooling unit, means when operative being adapted to vary the operation of the first means to cause a defrosting temperature of the cooling unit and being responsive-to a frosted condition of the cooling unit, retaining means for preventing the operation of the frost responsive means, and a time control device periodically operated for releasing the retaining means when the frost responsive means is operable in response to a frost condition of the cooling element.

10. A refrigerating system comprising in combination, a cooling unit, means for circulating refrigerant through said unit, control means operable to tend to maintain a predetermined temperature of the cooling unit, means when operative being adapted to vary the operation of the control means to cause a defrosting temperature of the cooling unit and being responsive to a frost condition of the cooling unit, retaining means for preventing the operation of the frost responsive means, and a time control device periodically operated for releasing the retaining means when the frost responsive means is operable in response to a frost condition of the cooling element.

EDWARD HEITMAN. 

